This script will update NoIP every 12hrs, or --frequency time, where time is the number of hours. It is recommended to use forever to restart the script if it crashes.
Example start command using forever: forever start -l forever.log -o out.log -e err.log app.js -u yourUsername -e yourB64PassHere -d your.domain.no-ip.org -s

To keep your NoIP password out of the bash history, you can prefix the command with a space. (This doesn't always work, credit to catonmat.com)

The script uses ICanHazIP.com by default to get your public IP address.